1. Field of the Invention
This invention relates to precision steel roller chains that are made to extremely close tolerances and that operate over sprockets. More specifically, the chains include roller links and pin links that are alternately arranged, and these links have laterally spaced side bars welded to each end of transversely extending bushings and pins, respectively. Rollers are mounted upon the bushings of the roller links, and these bushings have axial bores for receiving pins that connect the pin links to the roller links.
2. Description of the Prior Art
Sprocket chains of the bushing type have been constructed with two side bars and two bushings cast in one piece, to form a bushing link. Two of these bushing links are connected intermediately by two side bars in a manner that enables pivotal movement between links. Such chains are disclosed in U.S. Pat. Nos. 169,955 and 1,866,993.
In a type of sprocket chain known as a steel chain, the bushings are milled at their ends, and these ends are pressed into oblong holes punched in side bars to prevent the bushings from turning within the side bars. A bushing link, formed in that manner, has bushings that provide sufficient bearing area, on the connecting pins of pin links, to give the chain reasonable life. The connecting pins are generally milled at one end, or else provided with a lug, to prevent the pin from turning in the pin link side bars. Steel chains have also been made with bushing links, formed by separately constructed bushings that extend through side bars, to the outer sides thereof where the bushings are welded along their outer periphery to the outer surfaces of the side bars, as shown in U.S. Pat. Nos. 2,319,979 and 3,246,734. U.S. Pat. No. 2,512,429 shows a bushing with one end welded to an inner surface of a side bar and a pair of such bushings and side bars are oppositely arranged to form a bushing link.
It is desirable to reduce the weight and boundary dimension of a roller chain, while maintaining the basic ASA operating standards of roller width and pitch. Side bars, with bushings that extend through the side bar, must have a height that is dependent upon the diameter of the bushing. Pins, that project beyond the outer faces of the side bars of the pin links, determine the overall width of the roller chain, and it is one object of the present invention to provide a compact welded steel chain. Rollers, fitting about bushings, make it difficult to weld the bushings to the inner faces of the side bars, and bushings, fitting about pins, make it difficult to weld the ends of the pins to the inner faces of the side bars.